Tube machine



Oct. 7 1924. v 1,510,932

l J. F. GAn.

TUBE MACHINE v Filed Nov. e, 1920 4 sheets-sheet 2 m N llllmmV/ Q `Y 'l1| 'i lI/lIlIIIlIIlll/Illll//A Oct. 7 1924.

J. F1 GAILv TUBE MACHINE oct. 7, 1924. 1,510,932

J. F. GAlL TUBE MACHINE Film Nov. a. 1920 4 sheets-sheet 4 Patented Oct.7, 1924o `UNITED STATES JOHN F. GAIL, 0F IEIVANS'llOlI,l ILLINOIS.

TUBE MACHINE.

Application led November To all whom t may concern:

Be it known that I, JOHN F. GATT., a citi-l zen of the United States,residing at Evanston, in the county of (oo.k and State of Illiuois, haveinvented certain new and useful Improvements in Tube Machines, of whichthe following is a specification.

My invention pertains to several important and valuable novel featuresof structure,l

resulting in improved modes of functioning, in machines for producingmetal tubing or pipes having longitudinal Welded joints'y or seams fromsheets or strips of metal. Heretofore. appliances have been devised andused with a` moderate degree of satisfaction, in which the fiat metalstrip or blank as it is fed along is shaped or bent up transversely tocylindrical form with its longitudinal edges in abutting relation. suchlengthwise joint or seam being closed by Welding, as by means ofelectric heating, during the travel of the stock through the apparatus.

(treat difficulty has been experienced and much waste produced inattempting to use Isuch machines f or the production of tubes or pipesfrom relatively thin stock and the fused metal at the joint is not ofsuch density and closeness of structure as is desirable. In endeavoringto make comparatively' thin tubing in the known commercial machines, assoon as the metal along the joint becomes lsoftened or fused, thusmaterially reducing the resistance offered by the tube to lateralcontraction or collapse, there is great danger of the. edge portions ofthe metal along the joint becoming overlapped, which, of course. iswholly undesirable. rendering the product uusuited forits intended use.

One object of the present invention is to prov,ide a suitable machineWhich will efficiently and 'rapidly produce tubing from thin stockWithout danger of such edges becoming overlapped or displaced. I havefound that this may beaccomplished by so mounting and arranging theplurality of rollers or other members engaging and contiuing the tube atthe point of heating and .fusing that when the resistance vvhich thetube opposes to them is reduced by the softening of the metal of the.tube along the joint, by reason` of the electrically generated heat.such rollers or other corresponding elements cannot approach oneanother, which if permitted would decrease the aperture or throatthrough which the tube is passing s, 1920. serial N0.`422,41s.

causing the metal edges along the joint to override one another. Thepressure im osed by such rollers on the tube or pipe is o considerabl@amount and to eliminate the possibility of their moving inwardly towardone another and thus contracting the throat or opening through themachine, when the mechanical resistance of the tube is diminished underythe heat action, it is important that the mountings of such rollers beextremely rigid.' free from play, and incapable lof springing oryielding in the least degree. In fact, the play of the rollershaftsintheir bearings. even though the fits are as accurate and close as ,it ispossible to make them, is neutralized to tion specified. j

There is a tendency for the tubes or pipes produced by the machines nowin common use to have the fused metal at the joints somewhat porous incharacter, and one object of this invention is to supply means forcompressing or condensing such metal, at the same time reducing orleliminating entirely or in part the fin formed along the joints invpipes made in this manner.

A further purpose of the invention is the gradual heating of the meta-lof the blank to Welding temperature rather than extremely suddenlyproducing heat sufficient to effect the fusing or Weldin operation.

Another feature o the invention is to so form or shape the edges of themetal at the joint that they will originally have a Wi-dth of contactless than the thickness of the metal and preferably at the center ofsuch metal thickness, whereby the Welding Will occur at such middlesection and extend both inwardly and outwardly through the thickness ofthe. metal as the latter becomes thoroughly heated. Thus a progressiveWelding effect is secured with added advantages with respect to theuniformity of the heating and of the, density of the metal of the Weldedjoint. An additional object of the invention is the employment of theelectrical heatlng means to the best advantage. Without attempting toexplain the scientific theory 1nvolved in my 'novel machine, I yvlllmerely state that it has been my experience 1n the employment ofelectric Welding tube-makin machines, that the nearer the secondary othe transformer or the transformer itself is to the tube acted upon bythe current travprevent the undesired alc-i` ersing such secondarycircuit, the better the result secured. Ain advantage isfhad apparentlygreater thanthat derived solely from the reduction of the resistance ofthe secondary circuit beca-useof its shortened length. rirccordingly inmy type of tube machine the transformer is brought as near as possibleor feasible' to the point where the welding operation taires place. is asuggestion why such an arrangement is a distinct electrical advantage,but without confining or restrict ing myself to the theory advanced, lmay say that possibly the more or less rapid travel of the tube ofmagnetic material in close association with the transformer may havesome direct or indirect reaction thereon.

To enabie those skilled in this art to have a full and completeunderstanding of this invention both from structural and functionalstandpoints, and in order that such persons may comprehend the manner inwhich the above-stated and other desirable objects are secured by theemployment of this invention, l have illustrated a convenient embodimentof the invention, more or less diagrammatically, in the accompanyingdrawings forming a part of this specification and to which referenceshould be had in connection with the following detailed description,like reference characters referring to the same parts througl'iout theseveral views of such drawings,

In these drawings:

Figure 1 is aside elevation ,of the machine;

Figure 2 is a plan View of the same;

Figure 3 is avertical section through the tube adjacent to the weldingportion of the appliance with portions broken away;

Figure 4 is a plan view of the part of the machine shown in Figure 3with the transformer, with the exception of its brushes, removed;

Figure 5 is an enlarged elevation ot' the portion of the machine shownin Figure 3;

Figure 6 is avertical section through this portion of the apparatus nearthe tube traversing the machine;

Figure 7 is a vertical section on line7--7 of Figure 3;

Figures 8, 9, and 10 illustrate different pairs of forming rolls;

Figure 11 is an enlarged*y cross-section through lthe tube and itscontained water.

cooled mandrel Figure 12 is a longitudinal section through the tubeillustrating the manner of supporting the mandrel;

Figure 13 is a vertical section through the tube and mandrel;

Figure 14 depicts the rollerswhich form the edges of the metal strips;and

Figure Y15 is a fragmentary viewvcrosswise the joint portion of the tubeillustratinethe same on an enlarged scale.

-the particular structure depicted,

-eferring to theseV drawings, particularly rraeea ers 20,y 21 and 22geared together at 23 asV shown and driven or rotated from any suitablesource of power not illustrated, @if course, any other appropriate meansfor advancing. or feeding the tube or pipe, such as a draw-bench, may beempioyed instead of All. the other rollers are free to turn er revolveontheir own axes, or, in other words, they are not power driven. p

The metal for the formation of the tube or pipe enters the machine inthe form ot' a long, fiat blank or ribbon 24 of the proper width andleaves the applianceas a cornpleted tube or pipe 25 with a longitudinaiwelded joint.

Such metal strip first passes between a pair of forming rollers 26 and27 which bend or shape the sheet-metal body trans versely into the form28 shown in cross-seci tion in Figure 8. Such partially formed blankthen passes between a second pair of rollers 29 and 30 which stillfurther shape the metal. whereby it appears in cross-sec tion asillustrated at 3l in Figure il. Thereupon the strip or ribbon traversesthe third i pair of rollers 32 and 33 which deform it into the shapeindicated at 34 in Figure 10.

So far as now described there is nothing new in the apparatus.

llnstead of having both meetingedges of the metal at the longitudinaljoint in the tube or pipe flat or with plane surfaces as has heretoforebeen customary, in the use of this machine one edge 35 of suchpartiell;T formed tube 36 (Figures 11 and 15) is fiat and radiallydisposed with reference to the center or axis of the tube, but thecompanion or abutting edge is oppositelybeveled from its center linel 37providing two diverging or daring surfaces 38 and 39. The purpose ofthis arrangement is to secure an initial small area of contact'betweenthe edges to effect e'flicient heating and to initiate the weldingroperation at the center of the edges from which it spreads or extends inopposite directions both inwardlyand outwardly as the softening orfusing of the tube proceeds.

The next two pairs of rollers 40 and 4l. Figures 1, 2 and 14, are alikeand are designed to provide such surfaces on the edges ofthe sheetqnetalforming the tube, and they are slightly inclined to the vertical tobring the joint inv proper position with respect to the electricalcontact rollers and other parts of the heating or welding apparatus. i

The lower roller 41 of each pair has a face substantially semi-circularin cross-se(`- tion adapted to engage the lower part of the exterior ofthe tube, whereas the upper companion or complementary roller iscomposed of three elements or parts 42, 43 and 44 rigidly connectedtogether in any approved manner. The section 42 has atransversely-curved operative face of substantially 90 degrees, whereasthe corresponding face of the member 44 is somewhat less than 90degrees, the intermediate disc 43 having a lat surface 45 on one sidearranged radially with respect to the center of the partially formedtube, a flat surface 46 on the other side of the disc parallel to theface 45, and another falce 47 at an anu-le By drawing the tuv ev to thesurface 46, through these rollers and with its edges against theopposite faces of the middle disc, the surface 45 assures the productionon the corresponding edge of the metal of a radial, smooth, planesurface 35, while the surfaces 46 and 47 form the beveled or flaringfaces 38 and 39. The use of two pairs of such rollers-40 and 41 insuresthe production of the desired smooth surfaces onv the edges of the metalready for the fusing and welding operation.

Considering the electric heating and welding portion of the machinethrough which the metal strip or sheet now passes, it will be perceivedthat it includes a vertical concave roller 51 (Figure 3) and two,horizontal, concave rollers or discs 52 and 53, in the same plane, whichmay be located slightly in advance of the companion roller 51, unitedlyforming a throat o-r opening through which the tube isdrawn and of lessdiameter than the space between the rollers 41, 42 and 44, whereby thestrip in passing from the latter to the former group of rollers has itspreviously separated longitudinal edges not onlybrought into linecontact but the metal on both sides of the lengthwise gap is pressed orforced inwardly toward the opposed or companion edge to produce therequired upsetting to effect 'the desired welding or union of the edges.

It is. of great importance that these threeh revoluble rollers, of whichthe two horizontal ones 52 and 53 are electrical contact elements`suitably insulated, as may be required, designed to engage the tube onopp'osite sides of and close to its lengthwise jo-int, shall be veryrigidly mounted so that under no circumstances can they shift positionor app-roach one another to reduce or decrease the normal space betweenthem, otherwise there would be vgreat danger of the lmetal edges of thetube becoming overlapped, under the transverse pressure to which theyare subjected, as soon as they become softened or partially fused, whichis especially likely Lto happen if tubes or pipes of very thin metal arebeing produced.

To this end the roller 51 which has a curved or grooved face encirclingthe lower half of the tube is revolubly mounted by means .of a suitableshaft 54 in aligned beary a sliding bearing on the flat horizontal faceings 55 and 56 on a very substantial frame. 57 of which only a part isillustrated in the drawing. The two opposed, horizontal,slightly-separated rollers or discs 52 and 53 contact with thepartially-finished tube. on opposite sides of its lengthwise joint witha small space between their adjacent edges, the operative faceof eac-hof such rollers being curved on the same diameter or radius as theroller 51 so as to contact with slightly less than one-'quarter of thetransverse curvature of the tube. Thus it will be seen that, except forthe slight space between the rollers 52 yand 53, these three rollersentirely encircle` the tube forming a round opening of definite sizethrough which the tube is drawn by the action-of the feeding rollers 20,21 and 22.

As has been indicated, all of these three rollers must be so firmly'andrigidly mounted that under no circumstances shall they approach oneanother to reduce even in the smallest degree the space or openingbetween the rollers through which the tube passes. With this in view,the horizontal roller 52 is mounted on a'vertical shaft 58 revoluble ina bearing 59 in a block 60 adjustable horizontally lengthwise in aguideway 61 (Figure 7) pro-vided in one face of'an upstanding portion 62forming an integral part of the frame 57, the block 60 having a rib 63accommodated and slidable in such guiding groove 61. As is illustrated,the block 60, if preferred, may have 64 of a ,portion of the frame infront of .part 62.

In similar manner, the complementaryv electrical contact roller or disc53 is mounted on a vertical shaft 65 revoluble in a bearing 66 in ablock 67 lengthwise or longitudinally adjustable toward and from. thetube in the guide groove 61 in whichy its rib 63 its and is adapted toslide, the block, similar to the block 60, resting on and having asliding bearing on the face 64 of the main frame. l

In order to firmly bind and clamp these two 'blocks 60 and 67 in theiradjusted positions to the main frame so that under no circumstancescould they shift position vunintentionally, the machine is provided witha strap or bar 68 overlying the front faces,l of the two blocks andadapted to clamp .the latter to the upright portion of the main frame bymeans of a plurality of Abolts 69, 69 which when screwed up tightlyrender these adjustable blocks wholly immovable with respect to thesubstantial and solid mainV frame. Screw means may be employed ifdesired to secure accuracy and. nicety of adjustment of these slidableblocks relatively to one another in their guiding grooves while theclamp bar 68 is loose, but inasmuch as such screw means are the wellknown in many lines of industry., for.

simplicity in illustration, no attempt has been made to show them inthe'drawings.

ln actual practice the lengths of shafts 58 and 65 and their bearings 59and 66 would preferably be much longer than shown in the drawings andeven though such shafts fit their bearings as accuratelyv as it ispossible to make such constructions. it is, nevertheless. desirable ornecessaryv to eliminate the minute play between such shafts and theirbearings, and accordingly the upper end of each of such shafts isaccommodated in a bearing in the end portion of a member 71 adjustablyslidable on the top of the corresponding block 60 or 67` as the case maybe, by means of a pair of screws 72, 72 extendedpthrough threaded holesin lugs 73 upstanding frbm'the blocks 60 and 67, and bearing at theirends against the outer faces of the elements 71, two of the latter beingemployed, one for each of the horizontal rollers. Block 71 is providedwith a plurality of slots 74! extended vertically therethrough eachaccommodating a clamping screw 75.@ Each block 71 is forced inwardly byits-screws 72 whereby the outer half of its bearing 70 pressing againstthe l corresponding-portion of the upper part of the shaft 58 or 65forces `such shaft in-l size by reason of the rollers 52 and 53appreaching one another. Of course, there are many other mechanica-lexpedients for accomplishing thisresult, but l consider this portion ofthe invention of great im pol-tance because it renders possible themaking of tubes or pipes of this character out of relatively thin metalwithout danger of their longitudinal edges becomingoverlapped or thetube otherwise deformed.l

' lt is desirable also to prevent the rollers 52 and 53 changingrelation to or approaching roller 51 and accordingly they areprovidedfwith interlocking or gauge means performing this function.

short circuit'ing of the electrode or contact rollers 52 .and 53 by theintermediate lower roller k51, each of the "former isequipped.

with a thin layer or dise 151 of insulation material secured to itsbottoml face with its margin overlying and, if desired, in directcontact with thek adjacent 'side' cylindrical Wherefore, to 4.accomplishthis result andtalso to prevent remesa lpart of roller 51. Each element52 or 53 beneath such insulation disc has a cylindrical metal disc 152secured thereto with its circular margin above and bearing on thecylindrical yperiphery of a metalV disc `153 fastened to or Jformingpart of concave roller 51 and if desired its round edfe'mav khaving asingle turn secondary`77 in the bottom face of which are mounted anumber of contact brushes 78 bearing on the top surfaces of thehorizontal Contact rollers or discs 52 and 53, whereby to conduct theelectric current through such rollers t0 the tube to be welded.

ln advance of the points of contact of the rollers 52 and 53 with thetube, such secondary of the transformer is supplied with supplementarybrushes 79, Figure 6, contacting directly with the tube on oppositesides of its lengthwise joint, so that the metal of such jointissomewhat preliminarily heated before reaching the welding position,thus more or less gradually raising the heat of the metal to fusingtemperature.

At the region of heating, the tube travels over a liquid-cooled mandrel80 (Figures 11, 12 and 13), the cooling construction of which is shownmore or less diagrammatioally, which may or may not be of insulationmaterial, supported `by an arm 81 (Figure 12) mounted on any appropriatepart of the ymachine and extending into the interior of the v tubethrough its joint opening in advance of the place of closing the latter.The top and side faces of. such mandrel are rounded to correspond to theinterior curvature of the tube as shown indetail in Figure 11 and in thetop face ofthe mandrel a cavity or depression 82 is provided in which ismounted a revoluble pressure or backing-up roller 83 of insulationmaterial, glass for instance, l0-

cated in register with the joint of the tube. or

pipe. 1n order to be able to adjust such mandrel or core and its rollerup and down, that is toward and from the joint, a part at least of .thebottom of the mandrel is beveled at 84, Figure lll, and, beneath thisand shaped on its under surface to conform tothe correspondingVcurvature of the inner partof the lower pertiongof the tube, is awedgemember 85' with a screw adjustment 86 on the mandrel, so that byshifting this underf lying member lengthwise somewhat, the position ofthe mandrel properand its roller may be varied as may-,be required fromItime tot to time due to wear. The interior of the mandrel is supplied'4with flowing cooling liquid introduced in any appropriate manner asthrough one or more pipes 87. The mandrel proper. may or may not contactwith the inner surface of the tube, and in some cases it may bepreferable to have 'the cooling liquid flow through the tube beingformed rather than pass through the interior of the mandrel.I

Above the joint of the tube and at the point of welding is apressure-roller 88 of insulation material, and mounted in any approvedmanner preferably adjustable toward and from the joint, such roller atthe same time acting as a spacer for the contact rollers 52 and 53. Asillustrated, such roller is on the transformer and is adjustable up anddown to vary its position with respect to the tube joint and the inalong the tube pro duced by the welding operation. If preferred, suchroller maybe mounted on a suitable bracket rather than on thetransformer.

These two cooperating rollers 88 and 83 act to compress or condense thefused metal and prevent its becoming porous at the joint, at the sametime reducin or eliminating en tirelyv the fin along the joint broughtabout by the heating and welding operations.

The action of the machine occurs practically as follows: The long,`fiat, metalblank, by means of the feeding-rollers 20,- 21 and 22, iscaused to pass between the successive pairs of forming rollers 2627,l29-30, and 32-33 which gradually and progressively bend it uptransversely, whereupon itpasses to the two pairs of rollers 40 and llwhichshape its edges and bring them somewhat nearer together. Thereuponthe tube travels through the throat or opening formed by the threerollers 51, 52 and 53 with the 'joint portion between thepressure-rollers 88 and 83. rlhe electric current, traversing therollers 52 and 53 and derived from the transformer, heats the metal ofthe joint progressively inwardly and outwardly from the center of itsthickness to fusing or welding temperature, such parts having beeninitially or preliminarily heated somewhat by reason of the currentpassed through them by the advance 4brushes 79, and atv the same timesuch softened or fused metal is condensed or compressed by the upper andlower presser-rollers, the inner one being adequately cooled asspecified above. When the tube issues from the machine its lengthwisejoint is not only closed and sealed but the metal thereof is of firm anddense texture and the external iin is either absent or relatively vsmallin size.

Those skilled in this art will readily understand that this invention issusceptible of a ,vai-ietyl of embodiments and is consequently notlimitedto the precise and exact details of structure herein presentedbecause these notwithstanding the illustration and descrip,-

tion ofsome of the rollers as single elements, they may be made of aplurality of parts or separate rollers. I

I claim: y Y

' l. In a tube-welding machine of the character described, thecombination o-f more than two rollers unitedly forming an openingthrough which the metal tube blank is adapted to pass, means to causethe blank to tra\v'erse said opening, supporting means for said rollerspermitting them to revolve independently about their own axes, means topositively prevent said rollers from decreasing the desired size of saidopening, two of such rollers being positioned to engage the tube onopposite sides of its longitudinal joint, and means to pass an electricheating current through suoli two rollers and the tube joint to weld thelatter.

2. In a tube-welding machine of the character described, the combinationof a pair of rollers adapted to engage the tube undergoing formation onopposite sides of its longitudinal joint, means to cause the metal tubeblank to pass between said rollers, bearings for said rollers permittingthem to revolve independently about their own axes, means to positivelyprevent said rollers fromapproaching one another beyond a predeterminedpoint, and means to pass an electric heating current through saidrollers and the tube joint.

In a tube-making machine of the character described, the combination ofa roller positioned to engage the tube opposite its longitudinaljoint,.a pair of opposed rollers at substantially right angles to saidfirst roller and positioned to engage the tube on opposite sides of thetube joint at points in substantially the same plane as the contact ofthe iirst roller with the tube, means to cause the tube blank totraverse the opening formed I by said rollers, supporting means for saidthree rollers permitting them llO to revolve about. their own axes, andmeans to positively prevent said rollers from decreasing the size of theopening formed by them and through which tl'ie tube blank passes.

4. In aktube-welding machine of the charf i interesa 5. ln atube-welding machine ot the char-4 acter` described, the combination ofa roller positioned to engage the portion of the tube opposite itslongitudinal joint, a pair of opc posed rollers at practically rightangles to dit said first roller and positioned to engage the tube onopposite sides of said joint,at points in substantially the same planeas the contact of the first roller with the tube, means to cause thetube blank to traverse the opening formed by said rollers, means to passan electric heating current through said pair of rollers and the tubejoint between them, and means to positively pre-' vent all of saidrollers from decreasing the size of saidjopening. v

6. In al tube-welding machine of the character described, thecombination of a roller having a concave face substantiallysemicircularv in` cross-section and adapted to engage the half of thetube opposite its longitudinal joint, a pair of opposed rollers insubstantially the same plane and at `practically right angles to saidfirst roller and having concave faceseach of practically a quadrant of acircle in cross-section and positioned to engage the tube on oppositesides of said joint at points in substantially the saine plane as thecontact ofthe rst roller with the tube,4 means to cause the tube blankto traverse the opening 'formed by said rollers, means to pass anelectric heating .current through said pair of rollers and the tubejoint betweenthem, and means to positivelyy prevent all of said rollersfrom decreasing the size ot said opening.

V7. ln a tube-welding machine-ot the character described, thecombination of a pair of rollers in the same plane adapted to engage thetube on opposite sides of its longitudinal joint, shafts for saidrollers, bearings for said shafts, means to maintain said shafts withoutplay against the sides of such bearings nearest the tube, whereby therollers are.y prevented from decreasing the dis.

tance between them, means to cause the tube blank to pass between saidrollers, and means to pass an electric heating current through saidrollers and the tube joint'between them.

8. ln a tube-welding machine of the char acter described, thecombination-of a roller positioned to engage the portion of the tubeopposite its longitudinal joint, a pair oi opposed rollers atpractically right angles to said first roller and positioned to engagethe tube on opposite sides ot said joint at points in substantially thesame plane as the contact oi. the first roller with the tube, means tocause the tube blank toV traverse the opening formed by saidrollers,shafts for said pair of rollers, bearings for said 'shafts,means tomaintain said shafts withoutfplay against the sides "of such bearingsnearest the vtube,...whereby to prevent de crease of the distancebetween said pair ot rollers, and means to pass an electric heatingcurrent through said pair of rollers and the tube joint between them.

9.' lln a tube-forming machine oi the character described, thecombination of a -roller adapted to engage `the tube opposite itslongitudinal joint, a pair of rollers adapted to engage the tube onopposite sides ont said joint, overlapping discs interlocking l saidrollers togetherl to prevent decrease in the size oit the opening formedbythe rollers, and means to cause the tube blank to traverse saidopening.

l0. lin a tube-welding machine of the character described, thecombination of a roller adapted to engage the tube opposite itslongitudinal joint, a pair of contact rollers adapted to engage the tubeon opposite sides of said joint, overlapping discs interlocking saidrollers together to prevent decrease of the size of theopening'formed'by the rollers, means to cause the tube blank to traversesaid..opening, and means to pass an electric heating current throughsaid pair of rollers and the tube joint between them.

l1. In a tube-welding machine of the character described, thecombination of a roller adaptedv to engage the tube opposite itslongitudinal joint,a pair of contact rollf ers at right angles to saidfirst roller adapted to engage the tube on opposite sides of said joint,overlapping discs interlocking said rollers together to prevent decreaseof the size of the opening formed by the rollers, means to cause thetube blank to traverse said opening, and means to pass an electricheating current through said pair of rollers and the tube joint betweenthem.

12. lin a tube-welding -machine of the character described, thecombination of a roller adapted to engage the tube opposite itslongitudinal joint, a-pair of contact rollers at right angles to saidfirst roller positioned to engage the tube on opposite sides ofits'longitudinalljoint, shafts for said contact rollers, bearingsforsaid shafts, lmeans to maintain said shafts without play against thesides of such bearings nearest the tube, overlapping discs interlockingall of said rollers together, whereby the rollers are prevented fromapproaching one another and decreasing the o ning formed by them, meansto cause t e tube blank to traverse said opening, and means to ass anelectric heating curreiit through sai pair of rollers and the tube jointbetween them.

'13. In a tube-forming machine of the character described, thecombination of means to bend a stri of metal transversely into tubularform with a longitudinal joint at the lengthwise meeting edges of thestrip, means to shape an edge of the metal at the joint to have a widthof contact with the opposed edge of the metal less than the thickness ofthe metal, and means to cause the strip to traverse said bending landedgeshaping means.

14. In a tube-welding machine of `the character described, thecombination of means to bend a strip of metal transversely into tubularform with a longitudinal joint at the lengthwise meeting ed es of thestrip, means to shape an edge of t e metal at the joint to have a widthof contact with the opposed edge of metal less than the thickness of themetal, means to weld the edges of such joint together throughout thethickness of the metal, and means to cause the strip to traverse saidbending, edge-shaping and welding means.

15. In a tube-welding machine of the character described, thecombination of means to bend a strip of metal transversely into tubularform with a longitudinal joint at the lengthwise meeting edges of thestrip, means to shape an edge of the metal at the joint to have a Widthof contact with the op posed edge of metal less than the thickness -ofthe metal, means to electrically weld the edges of such joint togetherthroughout the thickness of the metal by passing an electric heatingcurrent across 'the joint, and

means to cause the strip to traverse said bendin edge-sha ing, andWelding means.

16. n a tubeorming machine ofV the character described, the combinationof means to bend a stri of metal transversely into tubular form with alongitudinal joint at the lengthwise meeting edges of the strip, meanstov shape an edge of the metal at the joint to have a width of contactwith the substantially central section of the opposed edge vof metalless than the thickness of the metal, and means to cause the' strip totraverse said bending and edge-shaping means.-

17. In a tube-welding machine of the character described, the4combination of means to bend a strip y into tubular form with alongitudinal joint at the lengthwise meeting edges of the strip,

of metal transversely 4means to shape an edge of the metal at the jointto have a width of contact with the substantially central section of theopposed edge of metal less than the thickness of the metal, means toweld the edgesl of such joint together throughout the thickness of themetal by heat electrically generated by a current traversing such joint,and means to cause the strip to traverse said bending, edge-shaping, andwelding means.

18. In a tube-forming machine of the character described, thecombination of a roller adapted to engage the longitudinal edges of ametal blank out of which the tube is made and to shape one of such edgeswith a plane surface substantially radially disposed with reference'tothe axis of the tube and shape the opposed edge of the. metal withsurfaces diverging from a longitudinal line substantially midway betweenthe inner and outer surfaces of the tube, and means to feed said blankpast said roller.

19. In a tube-forming machine of the character' described, a concaveroller having an intermediate disc' portion projecting beyond theconcave surface of the roller, and,

means to feed a metal'blank past the roller with its oppositelongitudinal edges bearing on and shaped by faces vof said projectingpart of the disc.

20. In va tube-forming machine of the character described, thecombination of a plurality of concaverollers each having an.intermediate disc portion projecting beyond the concave surface of theroller, and means to feed a metal blank past said rollers in series withits opposite longitudinal edges j bearing on and shaped by faces of saidprojec'ting parts of the disc portions.

21. Ina tube-welding machine of the cha1act'. described, the combinationof means to feed vthe tube longitudinally, a pair of contact rollerspositioned to engage .the tube on opposite sides of its longitudinaljoint, means to pass an electric heating current through said rollersand the tube joint between them, and an insulation spacing rollerbetween said contact rollers'.l

22. In a tube-welding machine of the character described, the'combination of means to feed the tube longitudinally, a pair of contactrollers positioned to' en 'age the tube on oppositesides of its long itumal joint, means to ass an electric heating current through said rollersand the tube joint between them, and an insulation spacing rollerengaging the tube joint `between said contact rollers.

JOHN F. GAIL.

